The tendency to form a stable foam is a known problem with known hard surface cleaning compositions. While the formation of foam is desirable with many personal washing products, such as shampoos, bath additives and bar soaps, the presence of foam is often undesirable in fabric washing and surface cleaning operations. As a consequence, considerable effort has been directed toward the investigation of antifoaming systems for fabric washing powders (so-called `Automatic` powders) and in low-foaming carpet and hard surface cleaners.
Antifoaming surfactant compositions are known which comprise mixtures of hydrophobic oils, such as silicone oils, together with particles, such as hydrophobic silica particles or occasionally alumina or titania particles. A large number of patents have been filed in this technical field. In practice antifoaming components are either added to the surfactant compositions during manufacture or shortly before use of said compositions. The step of adding the antifoam component just prior to use is more common with carpet cleaning compositions (which tend to be liquids) than with fabric washing powders. In washing powder technology it is virtually unknown in practice to mix components shortly before use. One reason for the late addition of the antifoam systems to liquid compositions is believed to be the tendency for insoluble particulate matter to settle out of solutions on storage. However, it has also been suggested, in GB 1407997 (P&G), that silicone antifoams are progressively deactivated if allowed to contact surfactants during processing and storage and complex encapsulation routes have been proposed to overcome these difficulties.
The use of hydrocarbons and calcium sensitive, fatty acid soaps as antifoam systems for powder compositions has been disclosed in GB 1099562 (Unilever: 1964). In that citation are disclosed powdered detergent compositions which comprise anionic sulphate or sulphonate detergents, alkaline polyphosphates and a `suds-depressant` mixture of a hydrocarbon and a fatty acid having from 12 to 31 carbon atoms. The hydrocarbon is broadly defined, as including straight or branched chain alkanes (liquid paraffin oils in 1:1 admixture with high melting paraffin waxes having a boiling point above 90.degree. C.), alkenes, alkylated benzene, condensed aromatics such as naphthalene and anthracene and their alkylated derivatives and alicyclic hydrocarbons, including terpenes and like compounds. Preferred hydrocarbons include those materials having a boiling point above 90.degree. C., such as the aforementioned mixtures of paraffin oils and waxes, dodecyl benzene and turpentine oil.
The use of the combination of solvents, soaps and selected terpene solvents as antifoam systems for liquid hard surface cleaning compositions is further disclosed in EP 0080749 (P&G: 1982). In these compositions, unlike the carpet cleaning compositions mentioned above, it is particularly desirable that the product can be used at will without the step of adding a separate antifoam component. More specifically, EP 0080749 teaches the use of mono (two isoprene units) or sesqui- (three isoprene unit) terpenes in combination with both a specified solvent (2-(2-butoxy-ethoxy) ethanol: available in the marketplace as BUTYL CARBITOL [RTM]) and 0.05-2% wt of one or more of the alkali, ammonium and alkanol-ammonium soaps of C13-C24 fatty acids as an antifoam system. In this citation, these three components are said to interact so as to have an antifoaming activity. The preferred terpenes as disclosed in this citation are the mono and bi-cyclic terpenes of the `hydrocarbon class` of terpenes such as terpinenes, terpinolenes, limonenes, pinenes and the so-called `orange` terpenes as obtained from the skins of oranges. Other terpenes including the terpene alcohols, aldehydes and ketones are less preferred.
Terpenes and related compounds suffer from the general disadvantage that they are odiferous compounds and generally lend a pine-like or lemon-like odour to products. It is desirable that the base formulation of cleaning compositions should have a low odour or be odour free. Moreover, it is advantageous for some uses that compositions should also be free of solvents such as butyl carbitol.